The metadata below describe the original scanning. Follow the "All Files: HTTP" link in the "View the book" box to the left to find XML files that contain more metadata about the original images and the derived formats (OCR results, PDF etc.). See also the What is the directory structure for the texts?
FAQ for information about file content and naming conventions.
"Facsimile ... made from a copy in the Yale University Library [originally published in 1798]"